Geotextile: a tightly woven fabric used to restrict the flow of fine soil particles and other contaminants while allowing water to pass freely through; used for protection of drainage systems from clogging.

Girt: a horizontal beam that supports wall cladding between columns.

Glass Felt: a sheet composed of bonded glass fibers, suitable for impregnation and coating in the manufacture of bituminous roofing and waterproofing materials, and shingles.

Glass Mat: a thin mat composed of glass fibers, woven or non-woven, with or without a binder. This mat may serve as reinforcement for certain roof materials and membranes.

Glaze Coat: (1) the top layer of asphalt on a smooth-surfaced built-up roof membrane; (2) a thin protective coating of bitumen applied to the lower plies or top ply of a built- up roof membrane when application of additional felts or the flood coat and aggregate surfacing are delayed.
(Also see Flood Coat.)

Gravel Stop: a low profile upward-projecting metal edge flashing with a flange along the roof side, usually formed from sheet or extruded metal. Installed along the perimeter of a roof to provide a continuous finished edge for roofing material. Acts as a bitumen-stop during mop
application of hot bitumen along a perimeter edge.

Groundwater Level: at a particular site, the level below which the subsoil and rock masses of the earth are fully saturated with water.

Grout: a mixture of cement, sand, and water used to fill cracks and cavities in masonry.

Grout (Non-Shrink): a cementitious material used to fill pitch-pans/pockets, prior to the application of a pourable sealer.

Gutter: a channeled component installed along the downslope perimeter of a roof to convey runoff water from the roof to the drain leaders or downspouts.